We investigated novel catalytic reaction systems which were activated by an electric field. This is the first report for the synergetic effect of catalyst and electric field. These catalytic systems showed very high activity compared to conventional catalytic reaction systems. Although Pt supported on CeO2 catalyst without an electric field showed no activity at 473K, the addition of an electric field to the catalyst promoted the degradation of ethanol. Pt/CeO2 catalyst was activated by the electric field and synergetic effect of Pt catalyst and electric field was observed. Thermal analyses showed that about 5–10% of input electrical power was wasted as a heat and about 90–95% was consumed for the endothermic reaction. Catalytic reactions in an electric field proceed under mild conditions and show a quick response.